1. Field of the Invention
The present invention relates generally to cotton harvester doffers, and, more specifically, to a method and mechanism for truing doffers to improve picker operation.
2. Related Art
In the mechanical harvesting of cotton with spindle-type picking units, the cotton is removed from the spindle by the doffer-mechanism including doffers or rotating discs having tangential velocity significantly greater than that of the picking spindle. As a spindle is moved under the face of the doffer disc, the motion of the doffer relative to the spindle unwraps cotton from the spindle, strips the cotton off of the end of the spindle, and propels the cotton into the conveying air stream. Because of the abrasiveness of the cotton fibers, the rubber or urethane coating of the doffer disc erodes. Since effective doffing action is a function of doffer to spindle clearance, the doffer must be regularly adjusted to compensate for doffer pad wear. If the doffer to spindle clearance exceeds 0.010 inch, doffing performance is affected and spindle wrap problems ensue. Also, the leading edges of the doffer lugs become rounded and the dull edges are less effective as sharp edges in removing cotton from the spindle. Depending upon variations in plant heights and varying distribution of the cotton bolls on the plant, the amount of wear of the doffer discs varies along the height of the doffer assembly. A high concentration of cotton imputed at a narrow range of height effectively wears a "hole" in the high wear zone. Spindles above and below the high wear zone are still close to the doffer, but clearance is excessive in the critical area of the doffer.
Previously, the only accurate means of truing a doffer was to remove it from the machine and place it in a special doffer grinding machine which cotton picker service departments must purchase or otherwise have available in the shop. Because of the time, inconvenience and expense of doing this, doffer truing is seldom done. Frequently an attempt is made to true a doffer by adjusting the doffer column down against the rotating picker spindles. Since the tangential velocity of the doffer is so much greater than that of the spindle, the doffer sees the rounded backside of the spindle barb instead of the sharp cutting edge. Hence the doffer is cut very inefficiently. Eventually, by heat and friction, the doffer can be worn away until it is trued, but the process exerts excessive force on the spindle bearings which results in premature spindle bushing deterioration. Providing a quick, simple, and effective means of truing a doffer assembly without removing the doffer from the machine and without spindle bearing wear has been a continuing problem.